Reproduction apparatus incorporating alternate redevelopment and reimaging cycles for multiple copies

ABSTRACT

A continuously operating transfer reproduction apparatus includes a cyclic control unit which automatically effects alternate redevelopment and reimaging cycles when reproducing multiple copies of the same master. An electrophotographic plate travels in a closed loop past a moving optical system which images the plate with a light image of the master creating a latent electrostatic image on the plate. The latent image is developed at a developing station and transferred to a substrate at a transfer station as the plate travels therepast. Increased throughput speed is achieved by effecting a fixed number of redevelopment cycles while the moving optical system is resetting. Thus, the plate continues its travel past the resetting optical system to the developing station where the latent image is redeveloped and thence to the transfer station for transfer of the developed image to a second substrate. The plate is then cleaned and charged prior to being reimaged with the light image of the same master, and the process continues until the requisite number of copies have been reproduced. In one embodiment, multiple imaging areas, preferably an odd number thereof, are located on the plate facilitating rapid alternate imaging and redevelopment cycles.

CROSS REFERENCE TO RELATED APPLICATIONS

The following application is assigned to the same assignee as thepresent application.

U.S. patent application Ser. No. 209,039 entitled "ElectrophotographicDevelopment Apparatus," Allison H. Caudill, inventor, filed Dec. 17,1971.

BRIEF BACKGROUND OF INVENTION

1. Field

This invention relates to an electrostatic transfer reproductionapparatus and, more particularly, to an improved control device thereoffor effecting rapid operation thereof.

2. Description of the Prior Art

In well-known continuous electrostatic printing processes, aphotoconductive surface is continuously moved in a closed loop pastvarious processing stations. Often, such systems include an imagingstation which incorporates a moving optical projection system whichprojects a light image of a master onto the moving plate therebycreating a latent electrostatic image thereon. The moving opticalprojection system scans the master in the direction of plate travel sothat the plate "sees" a continuous image of the master as it moves pastthe imaging station. The latent image on the plate is thereafterdeveloped at a developing station, and the image is transferred to asubstrate at a transfer station. When making multiple copies of the samemaster with such prior devices, it has been necessry for the system towait for the optical system to return to its initial position prior toautomatically initiating the second reproduction cycle. As devices havebeen constructed with ever increasing processing speeds, the delay timehas accounted for a substantial portion of each reproduction cycle.

Prior attempts to avoid the delay introduced by the resettng opticalprojection system have suggested redeveloping the electrostatic imagewithout reimaging the master. While such systems operate continuouslywithout a delay thereby occasioning a marked increased in throughput,the quality of the reproduced copies rapidly degrades as the number ofsuch redeveloped copies increase. That is, when a large number of copiesare required, the first several copies produced by redeveloping thelatent image without reimaging have virtually the same quality as thefirst copy produced by the system. However, each transfer operation andeach redevelopment operation tends to degrade the electrostatic latentimage on the plate thereby causing subsequent redeveloped copies todegrade in quality. Accordingly, the use of such a prior system wouldrequire operator intervention to reinitiate the system when imagequality degraded below that which the operator thought was good imagequality, thereby losing the time efficiencies of the redevelopmentprocess. Accordingly no commercially successful system utilizingredevelopment has been introduced since such systems are only effectivefor producing a relatively small number of high quality copies of thesame master.

SUMMARY

In order to overcome the above-noted shortcomings of the prior art andto provide a continuously operating electrostatic transfer reproductionapparatus having increased throughput speed when reproducing multiplecopies of the same master without degrading the quality of the outputcopy, the present invention incorporates a cyclic control unit whichautomatically effects alternate redevelopment and reimaging cycles whenreproducing multiple copies of the same master. In those embodiments ofthe invention wherein an odd number of image areas are located on thephotoconductive plate, the cyclic control unit initiates alternateimaging and redevelopment cycles. Thus, a given image area on the plateis first exposed to the light image of the master by the moving opticalprojection system and thereafter developed. The developed image is thentransferred to a substrate and the image area passes the imaging stationwhile the optical projection system is resetting. The originalelectrostatic image is redeveloped and the redeveloped image transferredto produce a second copy. The image area is then cleaned and chargedprior to again receiving the light image from the same master forproducing a third and fourth copy. The process continues until theRequisite number of copies have been reproduced. When an even number ofimage areas are located on the plate, the latent image is developedthree times (redeveloped twice) for each image exposure. Accordingly,the number of redevelopment cycles are automatically held to a minimumthereby assuring high quality copy output. Further, no delay times areintroduced by the resetting optical projection system since aredevelopment cycle is automatically taken while the optical projectionsystem resets. Thus, both increased throughput speed and goodreproduction output quality are attained without necessitating operatorintervention or judgement.

Accordingly, it is the primary object of the invention to automaticallyincrease the throughput speed of a continuously operating electrostatictransfer reproduction apparatus without causing an appreciabledegradation of output image quality.

A further object of the present invention is to provide a system of thisnature which rapidly reproduces a multitude of copies of the same masterwithout noticeable variations in image quality.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of the preferred embodiment of the invention as illustratedin the accompanying drawing.

In the drawings:

FIG. 1 is a schematic diagram of a continuously operating electrostatictransfer reproduction apparatus incorporating a cyclic control unit forautomatically effecting alternate redevelopment and reimaging cycles.

DESCRIPTION

Referring now to FIG. 1 of the drawings, a continuously operatingelectrostatic transfer reproduction apparatus incorporating a cycliccontrol unit is depicted.

The reproduction apparatus comprises a plurality of processing stationslocated about a cylindrically shaped photosensitive electrostatic plate11. The cylindrical plate comprises a layer of photoconductive materialsuperimposed over a conductive backing. A suitable photoconductivematerial is disclosed in U.S. Pat. No. 3,484,237, issued Dec. 16, 1969.The cylindrical plate is divided into three segments or framesdesignated A, B, and C. The frames are separated from one another byinterframe or intersegment gaps, a, b, and c.

A sensing device 13 senses permanently recorded signals within theinterframe gap portion of the electrostatic plate and supplies logicalsignals to a cyclic control apparatus to be described hereinafterindicating the positional relationship of the various frames withrespect to the various processing stations, as the electrostatic platesrotates in the direction of arrow 15 past the processing stations. Theelectrostatic plate 11 first passes a cleaning station 17 having anactuable cleaning member 19 located therein. When actuated, the cleaningmember 19 brushes the surfaces of the electrostatic plate 11 removingany foreign material including developer material therefrom. The platethen passes an actuable charging station consisting of a coronagenerating device 21 which sensitizes the electrostatic plate 11 as itrotates therepast. Thereafter, the electrostatic plate passes an imagingstation 23 which, when actuated, projects a light image of a master 25onto a frame segment of the electrostatic plate 11 rotating thereunder.The projection of the light image onto the sensitized electrostaticplate creates a latent electrostatic image thereon which rotates withthe plate as it passes the developer station 27. At the developerstation 27, multicomponent developer material including anelectrostatically charged toner is applied to the surface of theelectrostatic plate containing the electrostatic image thereon. Thecharged toner particles are preferentially attracted to the latent imageon the plate 11 and are subsequently transferred to a substrate surface29 at the transfer station 31.

As will be described hereinafter, the frame containing the latentelectrostatic image which had been imaged at the imaging station 23 isnot cleaned at the cleaning station 17 as it again rotates therepast,nor is it charged at the actuable charging station 21 as it againrotates therepast. Further, as will be described, the imaging station 23incorporates a moving optical projection system 33 which is reset to itsinitial position as the previously imaged frame rotates past the imagingstation 23. Since the initial latent electrostatic image remainsbasically in tact (it not being disturbed at the cleaning station 17 orthe charging station 21 or reexposed at the imaging station 23), theimage is redeveloped at the developing station 27 and the thuslyredeveloped image is transferred to a second substrate surface at thetransfer station 31. Thereafter, the segment containing the image iscleaned at the cleaning station 17, charged at the charging station 21and imaged with the same master 25 at the imaging station. The operationthus proceeds alternately imaging and redeveloping a previously imagedsegment until the requisite number of copies of the master 25 have beenproduced.

In the description immediately following, the detailed operation of eachof the processing stations located about the periphery of theelectrostatic plate 11 will be described. Thereafter will follow adescription of the cyclic control logic which effects the sequentialoperation of each of the stations as the electrostatic plate 11 rotatestherepast.

The sensing device 13 senses indicia permanently recorded on the edgeportion of the electrostatic plate 11 at the interframe gaps a, b and c.For example, this device could comprise a magnetic head adapted to readmagnetic signals recorded on the edge surface of the plate. The outputsignal of this device is utilized to control the sequencing of thevarious stations to be described hereinafter.

The cleaning station 17 incorporates as actuable cleaning member 19which moves from a position of close adjacency to the electrostaticplate 11 to a second position remote from the electrostatic plate 11.The cleaning member could, for example, comprise a cleaning brush wellknown in the art which intimately contacts the surface of theelectrostatic plate 11 and rotates there against, thereby removingforeign material including toner from the surface of the plate when inits position of close adjacency thereto. The magnet and armatureassembly 41 is actuated to drive the actuable cleaning member againstthe plate and the spring 43 returns the cleaning member to a position ofnonadjacency to the plate when the magnet and armature assembly isdeactuated. When in its position of nonadjacency to the plate, theactuable cleaning member 19 does not contact the surface of the plate,and therefore, the plate rotates therepast without interferencetherefrom.

The actuable charging station 21 comprises three corona generating wires47, 48, and 49 which are sequentially turned on and off as theinterframe gaps of the electrostatic plate 11 rotate therepast. Forexample, when the actuable charging station is turning on, the coronagenerating wire 47 is first energized as the first portion of aninterframe gap rotates therepast. The corona generating wire 48 is thenturned on as the same leading edge portion of the interframe gap rotatestherepast, and thereafter, the corona generating wire 49 turns on as theleading edge portion of the interframe gap rotates therepast. Thus, anydiscontinuities in charge levels effected by turning on the coronagenerating wires appear within the interframe gap portions of theelectrostatic plate 11. The same magnetic signal which is sensed by thesensing device 13 may also be utilized to actuate magnetically actuableswitches to effect the sequential turn on and turn off of the coronagenerating wires 47, 48 and 49. The turn off sequence of the actuablecharging station is identical to the turn on sequence.

The imaging station 23 comprises a fixed transparent document mountingmeans 55 onto which the master 25 to be copied is placed. A movingoptical projection system 33 projects a progressive light image of themaster 25 through the stationary lens 56 and aperture member 57 onto theelectrostatic plate 11 rotating therepast. The moving optical projectionsystem 33 includes a first carriage 59 and a second carriage 61, bothmounted in telescope fashion on a common track means 63 for reciprocalmovement. The first carriage 59 supports a lamp 64 and mirror 67 whichdirect light upon the master 25 through the slot 69 and documentmounting means 55 to thereby illuminate a segmental portion of themaster 25. A scanning mirror 71 is also mounted on the first carriage 59for receiving the image of the master thus illuminated.

The second carriage 61 supports a pair of compensating mirrors 73 and 75which receive the image as reflected by the scanning mirror 71 andredirect the image to the stationary mirror 77 through the stationarylens 56 from whence the image is reflected through the stationaryaperture member 57 onto the moving electrostatic plate 11. The firstcarriage 59 and the second carriage 61 are mechanically interconnectedthrough a closed loop flexible cable 79 to cause the movement of thesecond carriage 61 to be one-half of that of the first carriage 59. Bythusly moving the second carriage 61 by an amount equal to one-half thedistance moved by the first carriage 59, a constant optical path fromthe document mounting means 55 through the mirrors 71, 73, and 75 to thelens 56, mirror 77 to the electrostatic plate 11 is maintained duringthe motion of the first carriage 59, and the second carriage 61 in thescanning direction of arrows 81. The flexible cable 79 is mounted onrollers 83 and 85 carried by the second carriage 61. A ground clamp 87makes one point on the flexible cable 79 stationary at all times. Thefirst carriage 59 is connected to an intermediate point of the cable 79at point 89.

The motion in the scanning direction of arrow 81 is imparted to thefirst carriage 59 by the actuable drive motor 91 which is connected tothe capstan 93 which is in turn connected to the cable system 95. Asdescribed heretofore, motion of the first carriage 59 in the directionof arrow 81 effects motion of the second carriage 61 through theflexible cable 79 so that the second carriage moves one-half thedistance of movement of the first carriage. Upon completion of motion inthe scanning direction of arrow 81, the first carriage 59 and the secondcarriage 61 are returned to their initial home positions by the springmotor 97 which effects rotation of the capstan 93 in an oppositedirection thereby causing the cable system 95 to move the first carriage59 in the direction of arrow 99. The second carriage 61 is returned bythe action of member 59a of the first carriage 59 pulling the member 61aof the carriage 61 to its home position.

Summarizing, the scanning mirror 71 and an illumination system includinglamp 65, mirror 67, and slot 69 are driven by the capstan 93 insynchronism with the rotation of the electrostatic plate 11. As thescanning mirror 71 approaches the compensating mirror 73 thus tending toshorten the optical path, the compensating mirror 73 retreats atone-half the speed of the scanning mirror 71. Additionally, thecompensating mirror 75 also moves with the compensating mirror 73thereby creating a folded optical path which compensates for thetendency to shorten the optical path and maintains a constant opticalpath during the scanning operation. Accordingly, a light image of themaster 25 is progressively projected onto a frame of the electrostaticplate 11 rotating past the aperture 57 creating a latent electrostaticimage thereon. Once a complete frame section has been exposed, the lamp64 is turned off and the first carriage 59 and the second carriage 61are then driven to their home position under the control of the cablesystem 95. During the time that the optical system is returning andawaiting a new scan cycle, the next frame of the electrostatic plate 11rotates past the aperture 57.

As the electrostatic plate 11 passes the developer station 27,electrostatically charged toner is applied thereto thereby developingthe latent electrostatic image existing on the surface of theelectrostatic plate 11.

The operation of the developer station 27 is generally described in theaforereferenced copending application of Allison H. Caudill. Thedeveloper station includes a sump portion 111 containing multicomponentdeveloper material 33. The principle components of the developermaterial are electroscopic toner and a carrier material. Suitablematerials for use as toners are well known in the art and generallycomprise finely divided resinous materials capable of being attractedand held by electrical charges. Many well-known suitable carriermaterials can be utilized, the carrier particles generally being between50 and 1,000 microns in size. The carrier materials which are utilizedfor the developer station depicted must be ferromagnetic or capable ofbeing attracted and held by a magnetic field. Such a carrier materialcould comprise a magnetic bead coated with a material whichtriboelectrically interacts with the selected toner to produce a desiredcharge on the toner in order to provide good imaging quality.

A toner dispensing unit 115 is provided to dispense toner particles 117into the multicomponent developer material 113 located in the sumpportion 111 of the developer station 27. Counterrotating augers 119 and121 stir the freshly added toner with developer material to assurecomplete mixing thereof.

A bucket conveyor 123 rotates through the sump portion 111 of thedeveloper station 27 and scoops up quantities of developer material 113for delivery to the magnetic brush unit 125. The magnetic brush unitincludes a conductive, nonmagnetic, rotatable, cylindrical member 127having located therein a magnetic field producing means 129. Since thecore material of the carrier particles consists of a ferromagneticmaterial the carrier particles are caused to be magnetically attractedto the surface of the cylindrical member 127 and held thereon bymagnetic forces produced by the magnetic field producing means 129. Thecylindrical member 127 rotates in the direction of arrow 131 under adoctor blade 133 which governs the amount of developer material locatedon the surface of the cylindrical member 127 as it rotates to a positionadjacent the electrostatic plate 11. As described in the aforereferencedcopending application of Allison H. Caudill, the magnetic fieldproducing means 129 creates a normal magnetic field at approximately the9 o'clock position of the cylindrical member 127 causing the magneticcarrier particles in the developer material 113 to form in bristle-likearrays emanating from the surface of the cylindrical member 127.

The small toner particles of the developer material 113 are held ontothe surface of the relatively large carrier particles by electrostaticforces, which develop from the contact between the toner and the outersurface of the carrier particles which produces triboelectric chargingof the toner and carrier material to opposite polarities. A potentialsource (not shown) is connected to the cylindrical member 127 therebybiasing the cylindrical member to a fixed potential. As the magneticallyformed bristles of carrier material containing toner triboelectricallyattracted thereto rotate past and in contact with the electrostaticplate 11, the triboelectrically charged toner particles are attracted tothe electrostatic latent image on the plate 11 and adhere thereto. Thepotential on the cylindrical member correctly orients the electricalfield in which the charged toner particles move to produce a uniformlydeveloped image on the surface of the plate 11. The electrostatic plate11 containing a toned or developed image continues its rotationalmovement past the developer station 27 and continues to the transferstation 31. The carrier particles and the unspent toner particlesattracted thereto are retained on the surface of the cylindrical member127 until it reaches its approximate 6 o'clock position whereupon theyare released into the sump portion 111 for subsequent mixing and reuse.

As the developed image on the electrostatic plate 11 moves from thedeveloper station 27 toward the transfer station 31, a substrate surfacesuch as paper is fed from the hopper 141 by the picker roll 143 which isactuated in timed relation to the rotational movement of theelectrostatic plate 11.

The substrate surface 29 is fed over a feed path to the transfer roller145. The transfer roller comprises a conductive core 147 and adielectric outer layer 149. The conductive roll is biased so that thepositively charged toner particles will separate from the electrostaticplate 11 and transfer to the support substrate 29. That is, an electricfield is created between the grounded conductive backing member of theelectrostatic plate 11 and the biased core 147 through thephotoconductive surface of the electrostatic plate 11 and the insulatingmaterial 149 of the transfer roller 145. The toner particles move withinthis field to the support substrate 29 located between the electrostaticplate 11 and the transfer roller 145. Thereafter, the support substrateis removed from the surface of the electrostatic plate 11 by the pickoffmeans 151. The pickoff means 151 can comprise any of the well-knownpickoff devices utilized in the duplicator art such as timed air puffs,stationary guide members, or movable guide members. The thusly separatedsubstrate surface 29 containing a toned image is thereafter transportedto a fuser station (not shown) where the toner is fused to the substratein a well-known manner.

The description immediately preceding has related to the operation ofeach of the processing stations located about the rotating electrostaticplate 11. As described heretofore, various ones of these stations aresequentially actuated in accordance with the positional rotationalrelationship of the electrostatic plate 11 with respect to the fixedsensing device 13. The sequential actuation of the various stationsfacilitates alternate imaging and redevelopment cycles. By utilizingsuch alternate imaging and redevelopment cycles, the throughput speed ofthe reproduction apparatus is increased since there is no longer arequisite delay time occasioned by the moving optical projection system33 which must reset to an initial condition. Further, by limiting thenumber of redevelopment cycles, high quality output images aremaintained.

When utilizing an electrostatic plate having three segments such as thatdepicted in FIG. 1 of the drawings, alternate segments are first imagedon the first rotation of the electrostatic plate and the electrostaticlatent images created thereby are not thereafter substantially altered,thus allowing the latent image to be redeveloped on the secondrevolution of the electrostatic plate. The cleaning member and thecharging station are actuated prior to image cycles and deactuated priorto redevelopment cycles. The following table summarize the cyclicoperation of the cleaning, charging, imaging, and transfer stations.

                  TABLE I                                                         ______________________________________                                        Plate  Frame   Clean    Charge Image   Transfer                               ______________________________________                                        Rec.                                                                                 A       Yes      Yes    Scan    Yes                                                                   (image)                                        1      B       Yes      No     Return  No                                                                    (no image)                                            C       Yes      Yes    Scan    Yes                                                                   (image)                                               A       No       No     Return  Yes                                                                   (no image)                                     2      B       Yes      Yes    Scan    Yes                                                                   (image)                                               C       No       No     Return  Yes                                                                   (no image)                                            A       Yes      Same as                                                                              Same as Yes                                    3      B       No       Rev 1  Rev 1   Yes                                           C       Yes                     Yes                                           A       Same as  Same as                                                                              Same as Same as                                4      B       Rev 2    Rev 2  Rev 2   Rev 2                                         C                                                                      ______________________________________                                    

As can be seen from Table I, the operation on all even numbered platerevolutions is the same. After the first plate revolution, the operationof the device is the same for all odd-numbered plate revolutions, theonly difference between plate revolutions 1 and 3 being the operation ofthe cleaning and transfer stations with respect to the B segment whichdoes not go through a redevelopment cycle on the first plate revolution.

Referring once again to FIG. 1 of the drawings, the .[.machine.]. cyclecontrol logic which effects the cyclic operation of the cleaning,charging, imaging and transfer stations is depicted in block form. Thereproduction apparatus is started upon operator depression of a startcontrol 161. The operator also sets a copy counter 163 indicating thenumber of reproductions of the master 25 which are desired. Assumingthat a number of copies is specified, the copy counter 163 provides anoutput signal to the And gate 165 which provides a machine on signal.The machine on signal initiates the rotational movement of theelectrostatic plate 11 in the direction of arrow 15 and initiates thevarious processing stations in a well-known manner (e.g., the bucketconveyor 123 is rotated). When the indicia located in the interframegap, a, of the rotating electrostatic plate 11 is sensed by the sensingdevice 13, the frame counter 167 provides an output signal to the Andgate 169 which, in turn, sets latch 171. The frame counter 167 alsoprovides an output signal to the Or gate 173 upon sensing the indicialocated in the interframe gaps a, b, and c as they rotate past thesensing device 13. The output signal of the Or gate 173 and of the latch171 are provided to the And gate 175 which, in turn, provides a signalto the copy counter 163 causing that counter to be decremented. Thus,the copy counter is decremented as each segment rotates past the sensingdevice 13. It should be noted that the copy counter is initially setwith a number which exceeds the number specified by the operator byfour. This is to insure that the first rotational pass of segment B,which produces no copy, is not counted and that the last counted segmentrotates fully around to the transfer position. Thus, when the copycounter reaches a count of zero, the requisite number of copies havebeen reproduced and the machine is cycled off. It should further benoted that the output signal of the copy counter is utilized to preventcharging and scanning during the runout of the last copy.

The frame counter 167 also provides an output to the plate revolutioncounter 179 each time the interframe segment, a, passes the sensingdevice 13. The plate revolution counter provides an output signalindicating whether the electrostatic plate is in its first revolutionpast the sensing device 13 and, thereafter, whether the plate is in aneven or odd-number revolution. The output signals of the platerevolution counter 179 and of the frame counter 167 are applied to theAnd gates 180-183 which, in turn, are applied to the Or gates 187 and188 and the invertor 189. The output signal of the Or gate 187 isapplied to the cleaning control 192. The cleaning control 192 is furtherprovided with an input signal (not shown) indicating the preciserotational relationship of the electrostatic plate 11 with respect tothe cleaning station 17. As a segment of the plate to be cleaned rotatespast the actuable cleaning member 19, cleaning control 192 provides asignal to the magnet and armature assembly 41 causing the cleaningmember to contact the electrostatic plate 11. The signal remains onuntil the entire segment has passed the cleaning member at which timethe output signal of the cleaning control 192 is removed.

In a similar manner, the output signal of the Or gate 188 is provided tothe charge control 194 which is also supplied with a timing signal (notshown) indicating the exact positional relationship of the interframesegment with respect to the actuable charging station 21. The chargecontrol provides an output signal which effects the turn on or turn offof the corona generating wires 47, 48, 49 as the interframe segmentrotates therepast.

The output signal of the Or gate 188 is also provided to the scan andilluminate control 196. This control is also provided with a timingsignal indicating the exact positional relationship of the rotatingelectrostatic plate past the imaging station 23. The output signal ofthis device is supplied to the drive motor 91 which effects movement ofthe moving optical system in the scanning direction of arrow 81.Additionally, the output signal of the scan and illuminate control turnson the lamp 65 thereby illuminating the master 25. At the completion ofa scan, the output signal of the scan and illuminate control is dropped,thereby causing the lamp 65 to be extinguished and the enabling signalto be removed from the drive motor 91. The spring motor 97 effects thereturn of the moving optical projection system 33 in the direction ofarrow 99.

The Invertor 189 provides an output signal to the transfer control 198which is also provided with a signal indicating the positionalrelationship of the electrostatic plate 11 with respect to the transferstation 31. The output signal of the transfer control 198 effects therotational operation of the picker roller 143, thereby causing asubstrate surface 29 to be fed from the hopper 141 in time relationshipto the arrival of a developed image at the transfer station 31.

As described heretofore, the copy counter 163 provides a signal to thecharge control 192 and to the scan and illuminate control 194preventing, respectively the charging and scanning of unwanted segmentsduring a runout cycle. The same signal is provided to the cleaningcontrol 192 which effects cleaning of those segments which rotate pastthe cleaning station during a runout cycle.

It should be noted that the timing signals indicating the exactpositional relationship of the electrostatic plate 11 with respect tothe various stations supplied to the cleaning control 192, the chargecontrol 194, the scan and illuminate control 196, and the transfercontrol 198 may be provided by sensing devices similar to the sensingdevice 13 located at each station or by logic responsive to the sensingdevice 13 or by mechanical logic (e.g., cams, etc.) well known in theart. Further, the output signal of the cleaning control 192 may be heldon through an appropriate electronic delay device or by a mechanicaldelay. Additionally, the charge control is depicted as being responsiveto logic which turns on the actuable charging station 21. It should benoted that the absence of a signal from the Or gate 188 effects the turnoff of the actuable charging station as an appropriate interframesegment passes thereunder.

While the above description has related to a three segment electrostaticplate, it is, of course, recognized that a single segment plate could beutilized. In such an embodiment, the moving optical projection systemwould be actuated during a first revolution of the rotating plate andwould return to its home position as the plate rotated past the imagingstation during its second revolution. The cleaning member and thecharging station would be deactuated during the second pass of the platetherepast in order to facilitate redevelopment of the original image.

It should be further recognized that an even number of segments can beutilized by effecting two redevelopment cycles for every imaging cycle.Table II, set forth below, indicates the sequential operation of thevarious stations for a two-segment electrostatic plate.

                  TABLE II                                                        ______________________________________                                        Drum  Frame    Clean    Charge Image    Transfer                              ______________________________________                                        Rev                                                                                 A        Yes      Yes    Scan     Yes                                                                  (image)                                        1     B        Yes      No     Return   No                                                                   (no image)                                           A        No       No     Stationary                                                                             Yes                                                                  (no image)                                     2     B        Yes      Yes    Scan     Yes                                                                  (image)                                              A        No       No     Return   Yes                                                                  (no image)                                     3     B        No       No     Stationary                                                                             Yes                                                                  (no image)                                           A        Yes      Yes    Scan     Yes                                                                  (image)                                        4     B        No       No     Return   Yes                                                                  (no image)                                     ______________________________________                                    

From the above table, it can be seen that the moving optical projectionsystem remains stationary every third imaging cycle thereby allowing asecond redevelopment of a previously exposed latent image. The operationof the reproduction apparatus for drum revolutions 5-7 would beidentical to drum revolutions 2-4 and so on.

OPERATION OF THE INVENTION

Referring once again to FIG. 1 of the drawings, an operator places amaster 25 onto the document mounting means 55 and specifies a number ofcopies of the master to be reproduced by setting the copy counter 163.Thereafter, the operator depresses a start control 161 which gates theAnd gate 165 which in turn effects the rotational motion of theelectrostatic plate 11 in the direction of arrow 15. As the interframesegment, a, passes the sensing station 13, the frame counter 167provides an output signal effecting the decrementing of the copy counter163 and effecting the resetting of the plate revolution counter 179. Theoutput signals of the frame counter 167 and the plate revolution counter179 are provided to combinational gating circuits which in turn providesignals to the cleaning control 192, the charge control 194, the scanand illuminate control 196, and the transfer control 198. These units,respectively, control the sequential operation of the cleaning station17, the actuable charging station 21, the imaging station 3, and thetransfer station 31. Additionally, the developer station 27 is actuatedto provide a continuous flow of developer material 113 to the magneticbrush unit 125 which is continuously operated to develop electrostaticlatent images on the surface of the electrostatic plate 11 as the platerotates adjacent to the cylindrical member 27.

After the interframe segment, a, passes the sensing device 13, itthereafter passes an actuable cleaning member 19 which is actuated bythe cleaning control 192 to a position of close adjacency to the surfaceof the electrostatic plate 11. Thereafter, as the segment A passes theactuable cleaning member 19, residual toner existing thereon is swepttherefrom.

As the interframe sector, a, passes the actuable charging station 21,the magnetic indicia located thereon sequentially actuates the coronagenerating wires 47, 48 and 49 so that the charging station 21 applies auniform charge to the segment A as it thereafter rotates therepast. Whenthe interframe sector, a, reaches the imaging station 23, the scan andilluminate control 196 provides a signal to drive motor 91 and to thelamp 65. The drive motor 91 effects the movement of the first carriage59 and the second carriage 61 in the direction of arrow 81 in timedmovement with the movement of the segment A on the electrostatic plate11 past the aperture member 57, thereby projecting a light image of themaster 25 onto the surface of the electrostatic plate 11. Theelectrostatic latent image thus produced is developed at the developingstation 27 as the segment A rotates therepast. The transfer control 198initiates the feeding of a support surface 29 in timed relation to therotational movement of the segment A past the transfer station 31. Thedeveloped image on the sector A is transferred to the support surface 29at the transfer station 31.

As the interframe sector, a, again rotates past the sensing device 13,it provides a signal to the frame counter which in turn provides asignal that is utilized by the logic depicted to cause the cleaningcontrol 192 to deactuate the cleaning member 19 so that the cleaningmember does not engage the surface of the electrostatic plate 11 as thesegment A rotates therepast. Additionally, the charge control 194 causesthe corona wires 47, 48 and 49 to be turned off as the interframesegment a rotates therepast. As segment A of the electrostatic plate 11rotates past the imaging station 23, the signal is removed from thedrive motor 91 thereby allowing the spring motor 97 to effect the returnmovement in the direction of arrow 99 of the first carriage 59 and thesecond carriage 61 of the moving optical projection system 33. The lamp65 is turned off thereby insuring that the electrostatic image stillremaining on the electrostatic plate 11 remains undisturbed. Thereafter,the segment A passes the developing station where the latent image isagain developed and the transfer station where the transfer control 198effects the feeding of a second substrate surface 29 to receive thedeveloped image. Continued rotation of the electrostatic plate 11results in alternate imaging and redevelopment of the segment A.

The segment B of the electrostatic plate 11 which rotationally followsthe segment A is imaged by the moving optical projection system duringthose revolutions of electrostatic plate 11 that the image on thesegment A is redeveloped. In a similar manner, the segment B isredeveloped on those revolutions of the electrostatic plate during whichthe segment A is imaged or scanned. The segment C following the segmentB is imaged and redeveloped in a manner identical to that of the segmentA on any given revolution. As can readily be appreciated, for any givenplate revolution except the first revolution, three copies of the master25 are produced. When the requisite number of copies have beenreproduced, the copy counter 163 provides a signal causing thereproduction apparatus to turn off.

It should be noted that FIG. 1 is a schematic illustration and is notdrawn to scale. Thus, in actuality, the segment A is of a length equalto the length of travel of the moving optical projection system(assuming a 1:1 magnification ratio of the optical system).Additionally, the interframe segments are shown exaggerated in size forillustrative purposes. The interframe segment is not sufficiently largeto allow return of the optical projections system as the interframesegment rotates therepast. In fact, with an assumed processing speed of20 inches a second, and for the optical system depicted. the interframesegment must be approximately six times as large as the one required forcorona and cleaning station switching in order to "hide" the flybacktime of the optical system. Further, by utilizing a thickerphotoconductive layer, the requisite charging area can be reducedthereby further diminishing the width of the intersegment gap.

While the present invention has been described with respect to anoptical projection system incorporating moving mirror carriages, it willbe understood that the invention is equally applicable to thoseprojection systems utilizing rotational mirrors, travelling lenses,moving master document holders, and moving masters, each of which mustbe returned to an initial position prior to initiating a second imageprojection of the mounted master.

Further, as is understood by those skilled in the art, various charging,developing, transfer, and cleaning stations, per se, well known in theart could be utilized without departing from the spirit and scope of thepresent invention. Thus, for example, a cascade or screentypedevelopment system could be utilized. The cleaning station could alsoincorporate an actuable preclean corona and/or erase lamp which areactuated in the same sequence as the cleaning member described. Further,it has been found that, when utilizing a wiper cleaning member, thelatent image remains sufficiently undisturbed by the cleaning member toproduce a limited number of high quality copies even though the cleaningmember continuously remains in contact with the plate. Further, pressureand heat transfer techniques can be utilized, it being only importantthat the electrostatic image on the electrostatic plate be relativelyundisturbed by the transfer operation.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it should be understood bythose skilled in the art that the foregoing and other changes in formand detail may be made therein without departing from the spirit andscope of the invention.

What is claimed is:
 1. An electrostatic transfer reproduction apparatusincorporating an electrophotographic plate having at least one imagearea thereon which travels in a first direction in a closed loop past aplurality of processing stations comprising:mounting means for mountinga master for optical projection; an imaging .[.processing.]. station forprojecting a light image of said mounted master onto said image area ofsaid plate as said image area travels therepast creating a latent imageon said image area, said imaging .[.processing.]. station including; anactuable moving optical projecting system for projecting said lightimage while moving in said first direction from a home position;actuable drive means for moving said optical projection system in saidfirst direction from said home position and for returning said opticalprojection system to said home position; a developer .[.processing.].station for applying electrostatically charged developer material ontosaid image area thereby developing said latent image whenever said imagearea travels therepast; a transfer .[.processing.]. station fortransferring each developed image from said image area onto a substratewhen said image area travels therepast;an actuable .[.processing.].station actuable for removing a latent image on said image area as saidimage area travels therepast; position sensing means for sensing theposition of said at least one image area with respect to said processingstations; cycle control means responsive to said sensing means foractuating said optical projection system and said drive means when saidimage area travels past said imaging .[.processing.]. station on a firstpass thereby creating a latent image of the mounted master on said imagearea, for deactuating said actuable .[.processing.]. station and saidoptical projection system when said image area travels past saidactuable .[.processing.]. station and said image .[.processing.].station on at least one next subsequent pass following said first passthereby retaining said latent image created during said first pass andfor actuating said actuable .[.processing.]. station and said opticalprojecting system and drive means when said image area travels past saidactuable .[.processing.]. station and said imaging .[.processing.].station following said at least one next subsequent pass therebycreating a further latent image of said mounted master on said imagearea, the latent image on said at least one image area being developedat said developer .[.processing.]. station and transferred at saidtransfer .[.processing.]. station at least two times before removalthereof at said actuable .[.processing.]. station.
 2. The electrostatictransfer reproduction apparatus set forth in claim 1 wherein saidelectrophotographic plate having an odd number of image areas thereonand wherein said cycle control means alternately actuates and deactuatessaid actuable .[.processing.]. station and said optical projectionsystem when an image area travels past said actuable .[.processing.].station and said imaging .[.processing.]. station.
 3. Theelectrophotographic transfer reproduction apparatus set forth in claim 2wherein said electrostatic plate having an odd plural number of imageareas thereon.
 4. The electrostatic transfer reproduction apparatus setforth in claim 1 wherein said actuable .[.processing.]. stationincludes:an actuable charging station for charging said image area ofsaid electrophotographic plate when said image area travels therepast,said charging station being located prior to said imaging station insaid first direction of plate travel; said cycle control means actuatingand deactuating said charging station in the same actuation-deactuationsequence applied to said optical projection system when the image areatravels past said charging station.
 5. The electrostatic transferreproduction apparatus set forth in claim 1 wherein said actuableprocessing station includes:an actuable cleaning station for cleaningresidual developer material from said image area of said plate when saidimage area travels therepast, said cleaning station being located priorto said imaging station in said first direction of plate travel; saidcycle control means actuating and deactuating said cleaning station inthe same actuation-deactuation sequence applied to said opticalprojection system when the image area travels past said cleaningstation.
 6. The electrostatic transfer reproduction apparatus set forthin claim 1 wherein said drive means moves said optical projection systemin a second direction opposite said first direction when return saidoptical projection system to said home position:at least one of said atleast one image areas travelling past said imaging .[.processing.].station during the movement of said optical projection system in saidsecond direction.
 7. The electrostatic transfer reproduction apparatusset forth in claim 6 wherein said electrophotographic plate having anodd number of image areas thereon and wherein said cycle control meansalternately actuates and deactuates said actuable .[.processing.].station and said optical projection system when an image area travelspast said imaging .[.processing.]. station.
 8. The electrostatictransfer reproduction apparatus set forth in claim 7 wherein saidelectrophotographic plate having an odd plural number of image areasthereon.
 9. The electrostatic transfer reproduction apparatus set forthin claim 6 wherein said mounting means retains said master in astationary position and wherein said optical projection system includesa movable carriage for scanning said mounted master. .Iadd.10. Inelectrostatic transfer reproduction incorporating an electrophotographicsurface which travels cyclically around a closed loop past an imagingstation where the image of a master document is projected onto saidelectrophotographic surface, past a developing station for developingsaid projected images with electrostatically charged developer material,past a transfer station for transferring the developed image from theelectrophotographic surface to a substrate, past a cleaning station forcleaning developer material from the electrophotographic surface, andpast a charging station for charging the electrophotographic surface toa predetermined charge in preparation for the imaging station, apparatusfor hiding flyback time occurring at the imaging stationcomprising:means for sensing the position of frame on theelectrophotographic surface relative to said stations; means responsiveto said sensing means for indicating cycles of the electrophotographicsurface about the closed loop; optical projection means mounted withrelative movement between said projection means and the master document,said optical projection means responsive to said position sensing meansand said cycle indicating means for projecting at the image station animage of the master document on frames separated by at least one frameto allow said optical projection means time to fly back so that in agiven cycle of the electrophotographic surface around the closed loopimaged frames are followed by at least one non-imaged frame; saiddeveloping and transferring stations responsive to said position sensingmeans and said cycle indicating means for developing and transferringthe image from each imaged frame and each non-imaged frame carrying alatent image from a previous cycle of the electrophotographic surface;said cleaning and charging stations responsive to said position sensingmeans and said cycle indicating means for cleaning and charging thenon-imaged frames carrying a latent image during the cycle of theelectrophotographic surface in which the latent image is developed andtransferred for the last time before the frame is again imaged on thenext cycle whereby a frame on the electrophotographic surface is imagedin one cycle, and is passed over by the flyback of the projection meansin another succeeding cycle. .Iaddend..Iadd.11. The apparatus of claim10 wherein said electrophotographic surface contains an odd number offrames in the closed loop and each frame becomes an imaged frame and anon-imaged frame in alternate cycles of said electrophotographic surfacearound the closed loop. .Iaddend. .Iadd.12. Method for hiding theflyback time of an optical system used in an electrostatic transferreproduction apparatus wherein said apparatus has a charging station, animaging station, a developing station, a developed image transferstation, and a cleaning station past which an electrophotographicsurface moves cyclically in a closed loop, said electrophotographicsurface being of a predetermined size having an odd numer of imageframes consuming substantially all of the electrophotographic surfaceexcept for small interframe gaps to separate the frames, and saidoptical system and a master document to be projected mounted withrelative movement therebetween, the method comprising the steps of:sensing the cylindrical position of the frames relative to each of saidstations; actuating the optical system at the imaging station to imagethe master document on a first frame and every other frame thereafterand to fly back during an immediately succeeding frame and every otherframe thereafter; developing and transferring a developed image fromsaid first frame and every other frame thereafter during the firstelectrophotographic-surface cycle and from each frame during each cycleafter the first cycle of the electrophotographic surface through theclosed loop; cleaning and recharging a frame in theelectrophotographic-surface cycle during which the frame was not imagedwhereby each frame is imaged once and developed and transferred twiceduring two cycles of the electrophotographic surface through the closedloop and each frame is moved past the image station during optic systemflyback time, cleaned and recharged once during two cycles of theelectrophotographic surface in the closed loop. .Iaddend. .Iadd.13.Method for hiding flyback time of an optical system used in anelectrostatic transfer reproduction apparatus wherein said apparatus hasa charging station, an imaging station, a developing station, adeveloped image transfer station, and a cleaning station past which anelectrophotographic surface moves cyclically in a closed loop, saidelectrophotographic surface being of a predetermined size having an evennumber of image frames consuming substantially all of theelectrophotographic surface except for small interframe gaps to separatethe frames, and said optical system and a master document to beprojected mounted with relative movement therebetween, the methodcomprising the steps of: sensing the cyclical position of the framesrelative to each of said stations; actuating the optical system at theimaging station to image the master document on a first frame and everythird frame thereafter and to fly back during at least one frameintermediate the imaged frames; developing and transferring a developedimage from each frame during the first cycle of the electrophotographicsurface around the closed loop in which said frame is imaged andthereafter in each successive cycle; cleaning and recharging a frame inthe second electrophotographic-surface cycle during which the frame wasnot imaged whereby each frame is imaged once and developed andtransferred three times during three cycles of the electrophotographicsurface through the closed loop and each frame is moved past the imagestation twice without being imaged, cleaned and recharged once duringthree cycles of the electrophotographic surface in the closed loop..Iaddend.